肿瘤干细胞活体示踪的分子影像学研究进展

肿瘤干细胞(Cancer Stem Cell,CSCs)是肿瘤细胞中具有自我更新和多向分化能力的细胞,与肿瘤的发生、增殖、转移和耐药等生物学行为关系密切,CSCs的活体示踪对于实时监测CSCs在体内的生物学行为具有重要意义。目前常见CSCs活体示踪的分子影像学方法包括:超声成像、核磁共振成像(Magnetic Resonance Imaging,MRI)、光学成像、核医学成像(Positron Emission Tomography-Computed Tomography,PET-CT)、光声成像、多模态成像。这些成像方法的发展对于CSCs的研究具有重大意义,对于CSCs的研究有助于临床诊断及治疗,有利于诊疗一体化进程的发展。文章就CSCs活体示踪的分子影像学研究进展进行了综述。     

Molecular imaging perspectives.

Molecular imaging is an emerging technology at the life science/physical science interface which is set to revolutionize our understanding and treatment of disease. The tools of molecular imaging are the imaging modalities and their corresponding contrast agents. These facilitate interaction with a biological target at a molecular level in a number of ways. The diverse nature of molecular imaging requires knowledge from both the life and physical sciences for its successful development and implementation. The aim of this review is to introduce the subject of molecular imaging from both life science and physical science perspectives. However, we will restrict our coverage to the prominent in vivo molecular imaging modalities of magnetic resonance imaging, optical imaging and nuclear imaging. The physical basis of these imaging modalities, the use of contrast agents and the imaging parameters of sensitivity, temporal resolution and spatial resolution are described. Then, the specificity of contrast agents for targeting and sensing molecular events, and some applications of molecular imaging in biology and medicine are given. Finally, the diverse nature of molecular imaging and its reliance on interdisciplinary collaboration is discussed.     

Analytic evaluation of sampled aperture ultrasonic imagingtechniques for NDE

This paper presents a theoretical comparison of three generic sampled aperture ultrasonic imaging systems for nondestructive evaluation. The imaging systems are categorized according to their source-receiver combination for data acquisition: common-source, back-scatter, and full-array imaging. First, forward modeling is performed for a point source and a point receiver. This is then used to model the received data set for each of the imaging categories. Subsequently, the inversion algorithm for each category is derived, and their performance is evaluated in terms of resolution, noise, and computation. We show that in terms of resolution, back-scatter imaging is the best, followed by full-array and common-source imaging. However, in terms of material noise, full-array imaging is the best, with back-scatter and common-source imaging having the same material noise response. Full-array imaging is the only system with inherent redundancy to reduce electronic noise, but at the expense of significantly more computation. The physical transducer is in the full-array category, allowing mechanical scanning to be traded for dynamic focusing and computational power     

Evolution process from ghost diffraction to ghost imaging in a lensless imaging system

Ghost diffraction and ghost imaging are investigated in a lensless imaging system. The evolution process from ghost diffraction to ghost imaging is discussed when the object is moved far away from the source in the test arm. The relation of ghost diffraction and imaging is also studied, and it is found that the visibility of ghost imaging is always better than that of ghost diffraction.     

Tissue harmonic image analysis based on spatial covariance

The van Cittert-Zernike theorem has been widely used to describe spatial covariance of the pressure field backscattered from a speckle object. Spatial covariance contains important information in the context of correlation-based correction of sound velocity inhomogeneities. Previous work was primarily based on spatial covariance analysis for linear imaging. In this paper, we extend the analysis to tissue harmonic imaging. Specifically, we investigate effects of the signal-to-noise ratio (SNR) and sound velocity inhomogeneities on spatial covariance. Results from tissue harmonic imaging are also compared with those from linear imaging. Both simulations and experiments are performed. At high SNRs, although both linear imaging and tissue harmonic imaging have spatial covariance functions close to theory, the spatial covariance of tissue harmonic imaging is consistently lower than that of linear imaging regardless of the presence of sound velocity inhomogeneities. At low SNRs, on the other hand, spatial covariance of tissue harmonic imaging is significantly affected. Because the tissue harmonic signal is much weaker than the linear counterpart, the low SNR reduces the accuracy of correlation-based estimation. It is concluded that the linear signal is more suitable for correlation-based correction of sound velocity inhomogeneities, despite the fact that tissue harmonic imaging generally has improved image quality over linear imaging     

Extending the imaging volume for biometric iris recognition

The use of the human iris as a biometric has recently attracted significant interest in the area of security applications. The need to capture an iris without active user cooperation places demands on the optical system. Unlike a traditional optical design, in which a large imaging volume is traded off for diminished imaging resolution and capacity for collecting light, Wavefront Coded imaging is a computational imaging technology capable of expanding the imaging volume while maintaining an accurate and robust iris identification capability. We apply Wavefront Coded imaging to extend the imaging volume of the iris recognition application.     

柱面场景无畸变的折反射全景成像系统

提出了一种基于透视成像模型的柱面场景无畸变的折反射全景成像系统设计方法,该方法 利用系统柱面场景无畸变成像要求和视场角确定反射镜面形。根据这一方法设计制作了高次旋转对称非球面反射镜,并用该反射镜和CCD摄像头建立了全景成像系统,实现了对360°柱面场景的无畸变成像。     

分子影像学研究的进展和前景

医学影像学历经百年,终于从解剖结构为成像基础的传统医学影像学发展到了建立在一细胞、分子结构和功能为基础的分子影像学时代,这代表了医学影像学的未来,将对现代和未来医学模式产生划时代的影响。本文扼要介绍近年来世界各国在分子影像学研究方面取得的丰硕成果和展望其在未来的光辉发展前景。     

基于LED光源的成像板剂量性能初步研究

成像板的发光机制与光释光(OSL)元件的发光原理类似,均为光激励发光(PSL).为了验证光释光读出器也能用于成像板读数的可行性,使用丹麦Riso国家实验室生产的DA-15 OSL/TL通用读出仪开展成像板对光子和电子响应的测量研究.结果表明成像板的发光特性和剂量响应与释光类剂量计相同,使用光释光读出器对成像板进行测读可行.     

基于量子关联的显微成像研究进展

简要回顾了量子关联成像的基本原理和发展历程,从量子光源和经典光源的角度详细介绍了量子关联成像在显微成像中的研究进展。做出了基于经典源的量子关联成像因易于实施、成本较低,在显微成像中更具应用前景的判断。     

Elasticity imaging using conventional and high-frame rate ultrasound imaging: experimental study

High-frame rate ultrasound imaging is necessary to track fast deformation in ultrasound elasticity imaging, but the image quality may be degraded. Previously, we investigated the performance of strain imaging using numerical models of conventional and ultrafast ultrasound imaging techniques. In this paper, we performed experimental studies to quantitatively evaluate the strain images and elasticity maps obtained using conventional and high frame rate ultrasound imaging methods. The experiments were carried out using point target and tissue mimicking phantoms. The experimental results were compared with the results of numerical simulation. Our experimental studies confirm that the signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and axial/lateral resolution of the displacement and strain images acquired using high-frame rate ultrasound imaging are slightly lower but comparable with those obtained using conventional imaging. Furthermore, the quality of elasticity images also exhibits similar trends. Thus, high-frame rate ultrasound imaging can be used reliably for static elasticity imaging to capture the internal tissue motion if the frame rate is critical.     

CMOS APS图像传感器的像质分析

使用标准CMOS制作工艺生产的有源像素传感器（APS）引起了广泛关注。为了确定CMOS APS成像系统设计的主要参数选择的正确性,以及能否满足要求或指标,需要对相机系统的像质进行分析。考虑到CMOS APS图像传感器与CCD的不同,在分析时计算了CMOS APS成像系统中的镜头、滤光片和焦平面的调制传递函数（MTF）,系统MTF曲线为各个部分MTF值之积。在系统截止频率范围内,利用MTF曲线所围面积的大小来评价系统的成像质量。在系统制造之前,用调制传递函数作为像质的评价方法,看其是否符合使用要求,是十分有价值的工作。     

Strain imaging using conventional and ultrafast ultrasound imaging: numerical analysis

In elasticity imaging, the ultrasound frames acquired during tissue deformation are analyzed to estimate the internal displacements and strains. If the deformation rate is high, high-frame-rate imaging techniques are required to avoid the severe decorrelation between the neighboring ultrasound images. In these high-frame-rate techniques, however, the broader and less focused ultrasound beam is transmitted and, hence, the image quality is degraded. We quantitatively compared strain images obtained using conventional and ultrafast ultrasound imaging methods. The performance of the elasticity imaging was evaluated using custom-designed, numerical simulations. Our results demonstrate that signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR) and spatial resolutions in displacement and strain images acquired using conventional and ultrafast ultrasound imaging are comparable. This study suggests that the high-frame-rate ultrasound imaging can be reliably used in elasticity imaging if frame rate is critical     

Application of bispectral speckle imaging to near-diffraction-limited imaging in the presence of unknown aberrations

A laboratory experiment that demonstrates near-diffraction-limited imaging of a detailed object in the presence of unknown fixed aberrations in the imaging system is described. A random-phase plate is introduced in a pupil plane of the imaging system to eliminate the effect of fixed aberrations in the system. We employ a bispectral speckle imaging technique to recover the object from speckled images affected by both the random-phase fluctuations induced by the random-phase plate and the fixed aberrations present in the imaging system. For the case where the random phase is assumed to obey Gaussian statistics an approximate form of the bispectral speckle transfer function is obtained with an asymptotic expansion. This approximate form of the transfer function shows the diffraction-limited nature of bispectral speckle imaging when the standard deviation of the random-phase fluctuations is of the order of a wavelength of light. Experimental results are presented for fixed aberrations associated with lens tilt and defocus in the imaging system.     

Phase space representation of spatially partially coherent imaging

The phase space representation of imaging with optical fields in any state of spatial coherence is developed by using spatial coherence wavelets. It leads to new functions for describing the optical transfer and response of imaging systems when the field is represented by Wigner distribution functions. Specific imaging cases are analyzed in this context, and special attention is devoted to the imaging of two point sources.     

太赫兹成像技术在肿瘤检测中的应用

太赫兹(THz)波是频率位于0.1 THz^10 THz的电磁波。因其具有非电离性,以及可与多数生物分子产生共振响应等特性,在生物医学领域有着巨大应用潜力,尤其在肿瘤检测方面。太赫兹成像技术作为生物医学领域一种新的成像技术,吸引国内外多个研究小组对其开展深入研究。本文列举分析了多种太赫兹成像技术在肿瘤检测的应用,其中可分为太赫兹扫描成像、太赫兹层析成像、太赫兹全息成像以及太赫兹近场成像,介绍了这些成像方式的基本原理以及国内外研究现状,最后对太赫兹成像技术在生物领域的未来做出展望。     

多子阵双站合成孔径声纳成像算法

SAS测绘率是大面积海底测绘的一个重要指标,多子阵的方法已经在常规单站SAS的实际系统中取得了良好的效果。针对双站合成孔径声纳(双站SAS)测绘速率受空间降采样率限制的问题,该本文首先给出了发射站固定的双站SAS模型,分析了该模型双站SAS的测绘率。为了提高双站SAS的测绘率,本文中提出了发射站固定下的多子阵双站合成孔径声纳成像方法,并给出了严格的数学模型,形成了多子阵双站SAS系统设计方案,提高了系统的测绘率。文章最后给出了基于波束形成逐点算法多子阵双站SAS的成像仿真,仿真结果验证了方法的有效性。     

基于运动补偿的机械扫描式高频超声成像技术

由于高频相控阵超声成像系统和多阵元高频超声探头工艺复杂,成本较高、实现难度大,单阵元的机械扫描式高频超声成像探头因其结构简单、实现方便、成本低的特点仍具有较高的理论研究和实际应用价值。但目前机械扫描式成像系统的机械扫描的非均匀性是阻碍其性能进一步提升的主要问题,因此文章设计了一种高精度运动补偿的机械扫描式高频超声成像探头和系统,通过理论计算分析、运动系统结构设计加工、扫描成像系统搭建实现了高精度的扫描成像。最后,线靶和仿体的成像实验结果显示,经运动补偿后,系统能够有效克服传统机械扫描成像的伪影和失真,实现的横向几何位置精度误差为1.34%,纵向几何位置精度误差为1.33%,面积测量精度误差为3.15%,为高精度、高频超声成像算法和系统研究提供了一种有效的手段。     

In vivo optical imaging and dynamic contrast methods for biomedical research

This paper provides an overview of optical imaging methods commonly applied to basic research applications. Optical imaging is well suited for non-clinical use, since it can exploit an enormous range of endogenous and exogenous forms of contrast that provide information about the structure and function of tissues ranging from single cells to entire organisms. An additional benefit of optical imaging that is often under-exploited is its ability to acquire data at high speeds; a feature that enables it to not only observe static distributions of contrast, but to probe and characterize dynamic events related to physiology, disease progression and acute interventions in real time. The benefits and limitations of in vivo optical imaging for biomedical research applications are described, followed by a perspective on future applications of optical imaging for basic research centred on a recently introduced real-time imaging technique called dynamic contrast-enhanced small animal molecular imaging (DyCE).     

医用X线成像系统的数字化进展

医学影像技术是医学放射诊断学中最活跃的研究领域之一,而X线成像技术是医学成像的主要技术。文中介绍了医用X线成像系统由传统的成像方式向着数字化方向发展的过程中先后出现的CR、DR成像系统及其优缺点,着重论述了CR成像系统的改进和DR成像系统的关键部件-X射线探测器的种类并预测了X线成像系统的发展趋势。